1. Field of the Invention
The present invention relates to a new method for the oxidization of an oxidizable charge in the gaseous phase by a gas mixture containing at least one oxidizing gas, as well as a reactor for putting this method into practice.
It applies more especially to the slow and partial oxidization of oxidizable charges such as for example hydrocarbons for the preparation of synthetic gases comprising essentially carbon monoxide and hydrogen for the synthesis, for example, of methanol and higher homologous alcohol. It may be applied also, for example, to the oxidization of the vapor reforming effluents, of benzene, or to ammonoxidization reactions.
Although the oxidizing gases may include more than oxygen, ozone or the halogens, only the reactions with oxygen will be considered by way of example.
2. Description of the Prior Art
It is known to provide partial oxidization of methane, as indicated for example in U.S. Pat. No. 2,621,117.
The reaction takes place in a flame where the mixture of the gases is never perfect. Under these conditions, high temperatures are rapidly reached in the oxygen rich zones.
The gases produced at high temperature are then mixed in a zone rich in the charge to be oxidized and cause cracking of the molecules with formation of carbon likely for example to foul up the catalysts in the rest of the process and to reduce the efficiency of the reaction.
In the case of methane, production of carbon is observed and the synthetic gases must subsequently have the dust removed therefrom before use, for example for the synthesis of methanol from carbon oxides and hydrogen.
Besides the formation of carbon black, excessive overheating may occur of the zone where contact of the reactive gases takes place and in many cases these undesirable effects may be essentially attributed to the device for mixing the reactive gases at the inlet to the reactor, mixing of the gases being made at too slow a speed with respect to the gas phase reaction speed.
This is the case when the oxygen is injected through a single channel which must, moreover, have a sufficient section for admitting the whole of the flow and, although the gas is injected at high speed through this section, the speed of dispersion of the oxygen molecules is slow, compared to that of the reaction.
In addition, the oxygen jet, at the position where it leaves its orifice, is generally in the environment of the gas to be oxidized which flows at slow speed in the reactor,. This is not favorable to the rapid dispersion of the oxygen molecules.
The European patent EP 001 946 describes a reactor in which the oxygen, because of its high flow rate, is injected into the process gas through a multitude of parallel channels, each of these channels ending in an outlet orifice one at least of the dimensions of which is very much reduced, such as a slit whose width is preferably less than 8 mm.
In addition, in order to increase the dispersion speed of the oxygen in the process gas, this latter is driven with a violent helical movement around said channels, obtained by tangential injection of this gas on the inner walls of the apparatus.
Additionally U.S. Pat. Nos. 4,381,187 and 3,741,533 illustrate technological background of the invention.
Moreover, it is well known, particularly from the book by G. de Soete and A. Feugier: "Aspects physiques et chimiques de la combustion" Editions Technip, pages 87 to 93, to use the wall effect for reducing reaction speed and avoiding propagation of flame.
In the present case, the presence of pure oxygen and the high temperature implying a high thermal flow require flame arresting devices allowing the reaction to continue without explosion, while being within explosive limits (particularly in the case of the partial oxidization of methane).
The objectives which it is proposed to obtain and which correspond to the problems raised by the prior art are essentially the following:
an oxygen and charge distribution zone of a reactor adapted to a substantially homogeneous perfectly controlled mixture between the oxygen and the charge to be oxidized. This distribution zone must be particularly adapted to the rapid dispersion of the oxygen molecules. PA1 "flame arrest or quenching", avoiding explosion and yet allowing the operation to be carried out at temperatures which may reach more than 1000.degree. C., with the object of protecting the reactor and a mixing device from the excessive heat released during partial oxidization. PA1 a) the oxidizable charge and the oxidizing gas are caused to flow simultaneously in a distribution zone made from a ceramic material comprising at least one row of channels of a first type or group so that one of the two gases formed respectively by the oxidizable charge and the oxidizing gas flows separately inside said row and so that the other gas flows separately outside said row, the oxidizable charge and the oxidizing gases flowing through at least a part of said zone and advantageously in the vicinity of the outlet, a multiplicity of spaces with passages having, at least in one direction, a dimension at most equal to 10 mm corresponding to the quenching distance of the flame which may result from the oxidization of said charge by said oxidizing gas, PA1 b) then said oxidizable charge and said oxidizing gas are mixed, thus distributed in the mixing zone made of a ceramic material defining a multiplicity of spaces having passages with, at least in one direction, a dimension comparable to that of the passages of step a), and PA1 c) the mixture of products from step b) is caused to react in a ceramic material reaction zone having a multiplicity of spaces, with passages having, at least in one direction, a dimension comparable to that of the passages defined in steps a) and b), the distance between the distribution zone and the mixing zone on the one hand and the mixing zone and the reaction zone, on the other, being at most equal to said quenching distance of the flame.